Maternal Age and Urinary Incontinence Risk:
Review of Recent Epidemiology
A. Hijaz MD.
T
he International Continence Society (ICS) defines urinary incontinence as the complaint of any
involuntary leakage.1 The prevalence of urinary incontinence in community-dwelling women ranges from
10% to 40%; wider ranges can be found in elderly women.2 In studies that differentiate any urinary
incontinence from severe or daily disease, the prevalence was 29% (range 11%–72%) and 7% (3%–
17%), respectively.3 About a quarter of urinary incontinence is regarded as severe.4 Prevalence has
always been higher in institutionalized subjects. Several recent studies from around the world suggest a
prevalence of ≥ 50%.2 Approximately half of all incontinent women are classified as stress incontinent,
making this group the largest among urge, mixed, and stress types.3
The pathophysiology of stress urinary incontinence (SUI) is multifactorial and involves genetic, inciting,
promoting, and decompensating factors.5 Development of SUI is strongly associated with pregnancy,
maternal age, vaginal delivery, and aging. 6-8 Vaginal delivery can injure the nerve, muscle, and
connective tissues responsible for maintaining continence.9 However, the injury alone does not explain
the entire picture on pathophysiological mechanisms of SUI. Clinical and experimental data suggest that
recovery—or lack thereof
(decompensation)—from injuries following childbirth trauma is as significant to the pathophysiology of
SUI. Approximately one third of women develop SUI following delivery,8,10 but in most women this resolves
within a year.11 This process continues: even among women who have full remission of SUI after delivery,
almost half redevelop SUI 5 years later7 and over half develop SUI decades later, near the time of
menopause.12 Understanding the mechanisms mediating the balance between injury and recovery
appears to be the key in understanding the role of promoting and decompensating factors in
pathophysiology of SUI.
Data from the obstetrical literature reveal that more and more women are having their first deliveries at
an advanced maternal age. A significant body of evidence has emerged emphasizing the role of maternal
age at the time of first pregnancy as an independent risk factor for the occurrence of SUI. The purpose of
this article is to review the epidemiological data that support the role of advanced maternal age in the
development of SUI, using evidence from both retrospective and prospective short- and long-term
epidemiological studies.
Evidence from retrospective
studies and case series
In a retrospective study to examine
the prevalence of postpartum SUI, Groutz et al demonstrated a four-fold increase in SUI prevalence 1–2
years after spontaneous delivery in older compared to younger primiparae (38.5% vs. 9.8%, respectively;
P < .001).13 In addition, elderly primiparae who underwent elective cesarean section had a significantly
lower prevalence of postpartum SUI than those delivered vaginally. Fritel et al conducted a retrospective
survey of cases 4 years after first delivery, revealing 29% (89/307) prevalence of SUI.14 According to
multiple logistic regression analysis, the independent risk factors for development of urinary incontinence
were urine leakage before the first pregnancy (odds ratio [OR] 18.7; 95% confidence interval [CI], 3.696.4), urine leakage during the first pregnancy (OR 2.5; 95% CI, 1.3-4.8), duration of first labor ≥ 8 h (OR
3.1; 95% CI, 1.7-5.7), mother’s age > 30 years at the first delivery (OR 2.4; 95% CI, 1.4-4.2) and
cesarean section at the first delivery (OR 0.3; 95% CI, 0.1-0.9). The main risk factors identified were
maternal age, previous incontinence (before or during the first pregnancy), prolonged labor, and vaginal
delivery. Urinary leakage before or during the first pregnancy seemed to be an early risk factor; however,
this result must be interpreted cautiously because of the retrospective nature of data collection. The
relationships that were observed between urinary leakage before or during the first pregnancy and SUI 4
years later might be partially explained by a recall bias.
On the other hand, young age at first delivery was described as a risk for severe SUI in
perimenopausal women. Fritel et al reported a cross-sectional study of 2625 perimenopausal women that
examined the prevalence of severe SUI and potential obstetric risk factor.15 This study demonstrated that
women with age at first delivery < 22 years had a higher risk of severe SUI. It also demonstrated that the
risk of severe SUI increased with body mass index (BMI), diabetes, and previous urinary incontinence
surgery. The risk of SUI was higher among parous than nulliparous women. Neither the mode of first
delivery nor the mode of all deliveries was associated with severe SUI, in contrast to other studies that
found cesarean delivery had protective effect against SUI.
Grodstein et al also found first delivery at a young age to be a risk factor.16
The investigators assessed obstetric history among participants of the Nurses’ Health Study through the
use of biennial mailed questionnaires from 1976 to 1996. In that final year, 83,168 women aged 50 to 75
years reported their frequency of leaking urine and quantity leaked. Over all, 34.1% of the women
reported leaking urine at least once per month during the previous
12 months. After controlling for potential confounders, there were strong trends of increasing prevalence
of occasional and frequent leaking with increasing age (P < .0001). There was also increasing prevalence
of leaking urine with increasing parity. Age at first birth of > 35 years was associated with a slight
elevation in frequent leaking compared with women with age at first birth from 21 to 25 years (OR 1.13;
95% CI, 0.94-1.36). It is interesting that Grodstein et al observed greater elevated risks of incontinence
among women who gave birth at the youngest ages compared with those women who first gave birth at
21 to 25 years; for those aged < 20 years at their first births, the risk of frequent leaking was 1.27 (or 1.27,
95% CI,13-1.42).The last 2 studies differ from the first 2 in that they reported on severe or frequent
incontinence and, more important, they examined the risks in a later time frame from the time of delivery.
Evidence from prospective short term studies
Glazener et al recently reported a large epidemiological study in which all women who delivered over
the course of a year in 3 maternity units were asked to complete a mailed questionnaire 3 months
postpartum. 17 Of 10,989 eligible women, 7879 (72%) completed the questionnaire, and 3405 of them
were primiparae with singleton births. The prevalence of incontinence among the 3405 primiparae was
29%. The study demonstrates that the mode of delivery and older maternal age were significantly related
to the chance of developing new urinary incontinence 3 month after delivery. The likelihood increased
most for the oldest women (35 years and over). The likelihood of incontinence after a cesarean section
was about three-fold lower.
Maternal age was not a significant factor in women whose incontinence first occurred during pregnancy.
In these patients, body size and the weight of the baby were significant risk factors, and C-section
remained associated with lower rate of incontinence. Maternal age was a significant factor only for
incontinence that first occurred after delivery, not during pregnancy.
Maternal age was an independent risk in 3 other prospective short-term studies following delivery.
Schytt et al investigated stress incontinence 1 year after childbirth and found that there was increased
prevalence of incontinence with increasing age among primiparous women.18 Van Brummen et al in a
prospective study
examined the severity of both SUI and
overactive bladder symptoms during and 1 year after the first pregnancy.19 The study demonstrated that
the predictive factors for presence of bothersome SUI were greater maternal age (32.5 vs 30.3 years old
at delivery) and the presence of bothersome SUI at 12 weeks of gestation. The authors also confirmed
results from a previous study that cesarean section seems to be protective of bothersome SUI. To obtain
an insight into the role of age on bothersome SUI, they analyzed age divided into 4 groups, 26–30, 31–35
and ≥ 36 years); none of the women aged 25 years, 2.8% of those aged 26–30 years, 4.3% of those aged
31–35 years, and 10.3% of those aged
≥ 36 years had bothersome SUI. Using those aged < 26 years
as the reference group, there was a trend for women aged > 30 years to have more bothersome SUI (P <
0.098).
Baydock et al recently reported on the risks of urinary incontinence 4 months after vaginal delivery in
632 patients; 29% had any urinary incontinence.20 Univariate analysis showed that stress incontinence
was increased in patients ≥ 30 years of age
(26.2%) compared with patients < 30 years of age (19.3%) (RR 1.4; 95% CI, 1.0-1.8; P = .05). In
multivariate analysis, the 2 variables that remained significant for any urinary incontinence were maternal
age ≥ 30 years (P < .01) and forceps delivery (P < .01).
Evidence from long-term prospective studies in a six-year followup study on the cohort reported by
Glazener et al and described above, MacArthur et al reported that women older than 35 years at first birth
had 2.36 higher odds of developing SUI 6 years following the index delivery compared to women younger
than 25 years.21 Of the original cohort of 10,989 eligible women, 4214 (38%) completed a followup
questionnaire 6 years later. Older maternal age at first birth (> 30 years), parity, and vaginal delivery were
significant risk factors for persistent (defined as incontinence at 3 months and 6 years) and long-term
urinary incontinence (defined as incontinence at 6 years but not 3 months). The prevalence of persistent
urinary incontinence (at both 3 months and 6 years) was 24%. Point prevalence had increased from 33%
at 3 months to 45% at 6 years. Among women symptomatic at 3 months, the proportion who still had
symptoms at 6 years was 73%; this rate was similar among the index primiparae (71%). Among the
women without symptoms at 3 months, symptoms at 6 years were reported by 33% of those who had
subsequent births and 30% of those who did not.17
A logistic regression model restricted to primiparae at index birth showed that inclusion of the
additional obstetric variables did not alter the associations with mode of first delivery, maternal age,
number of births, or ethnic group. Symptoms were less likely with a first delivery by cesarean section (OR
0.36; 95% CI, 0.25-0.53) and there were no associations with forceps (OR 1.00; 95% CI, 0.75-1.35) or
vacuum extraction (OR 1.11; 95% CI, 0.77-1.61). None of the additional obstetric variables showed
associations with persistent urinary incontinence. Only pre-pregnancy BMI was associated, with women in
the heaviest quartile (BMI ≥ 25) reporting more symptoms (OR 1.55; 95% CI, 1.08-2.22).
Viktrup et al conducted a longitudinal cohort study to examine the impact of onset of SUI, in first
pregnancy or postpartum period, for the risk of symptoms 12 years after the first delivery.8 The study
demonstrated that the presence of SUI 3 months after first delivery predicted a very high risk of SUI after
5 and 12 years. The study confirmed the finding that onset of SUI during first pregnancy or puerperal
period carried a risk of inducing instant or delayed SUI that may become chronic and be present 5 and 12
years later. This study also showed that even if women with SUI during first pregnancy had cesarean
delivery, they had a higher prevalence of symptoms 12 years later than women without SUI during
pregnancy who delivered vaginally. Obesity before first pregnancy and delivery seemed to increase the
risk of SUI that may become chronic and remain 12 years later. Breastfeeding for more than 6 months
after first delivery was found to reduce the risk of long-term SUI 12 years later. In Viktrup’s analysis, there
was no statistically significant difference in the prevalence of SUI at 12 years in women ≤ 25 or > 25 years
at first delivery.
Rortveit and Hunskaar studied the effect on urinary incontinence of maternal age at first and last
pregnancy.22 Their main conclusion was that being older than 25 years at the first delivery increases the
risk for urinary incontinence, and specifically stress incontinence, compared with being younger. The
prevalence of any urinary incontinence was significantly higher among women who had their first delivery
after the age of 25 years compared with women who had their first delivery at the age of 25 years and
younger (27.7% vs 23.2%, P < .01). However, the effect attenuated with
increasing actual age and it disappeared in the age group 50–64 years. The age at the last delivery
seemed to be of less importance.
In a prospective observational study over 10 years, Altman et al assessed the long-term effects of
childbirth on urinary incontinence after first delivery. 23 They demonstrated a significant increase in
prevalence of SUI as well as urinary urgency at 10 years followup. The relative risk (adjusted for maternal
age and parity) of moderate to severe urinary incontinence increased significantly 10 years after first
delivery (RR 5.8; 95% CI, 1.2-33.7). Multivariable regression analysis on obstetric covariates at first or
subsequent deliveries showed no significant association with the development of SUI or urinary urgency
at 10 years followup. Multivariable analysis (adjusted for age and parity) revealed that SUI symptoms at 9
months and 5 years followup were independently associated with the presence of symptoms at 10 years
(RR 13.3; 95% CI, 3.9-33.1 and RR 14.1; 95% CI, 2.5-18.8, respectively). The investigators could not
confirm that maternal age at the time of first delivery was associated with an increased risk for urinary
incontinence.
Conclusion
The body of evidence from retrospective and prospective studies suggests that advanced maternal age is
an independent risk factor for the development of SUI. This effect might be attenuated with time from the
index delivery and with the severity of incontinence. The biological explanation for this observation is
extremely intriguing. The clinical implication is also important as more and more women are having their
first child at an advanced age. Does advanced age affect tissue susceptibility to trauma or tissue
recovery? This has been the focus of our translational research utilizing an animal model of simulated
birth trauma, and vaginal distension. We have recently demonstrated that aged rats subjected to vaginal
distension have evidence of delayed recovery compared to young rats (unpublished data). Future
research in our laboratory will explore the mechanistic
relationship between aging and delayed recovery.
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